Scientists were amazed after workers at a construction site near San Diego unearthed the bones of a number of prehistoric Ice Age animals, including ancient mammoths that could be up to 200,000 years old.

The bones were discovered in a new housing development meant for hundreds of new homes in Carlsbad, and the fossils are dated to the last Ice Age, which means they are at least 50,000 years old but could be 200,000 years old, according to a San Diego Union-Tribune report.

In addition to the mammoths, experts also found a prehistoric bison — for only the second time in San Diego County — as well as the bones of ancient horses and turtles. These bones could be a treasure trove of information about the climate and environment during that time period. It could also tell scientists about the ecology of that area and how the ancient ecosystem function, providing clues on climate change.

Workers made the discovery while grading at the Quarry Creek development site this summer. Thanks to California state law, a paleontologist was on hand because it was a large building project involving hundreds of new homes that would require a lot of earth to be moved. When the bones were discovered, work immediately halted to allow for excavation.

For the time being, the bones will call a local museum home where they will be put on display until a more permanent home can be found. Workers encased the bones in plaster in order to transport them safely.

The findings included two Columbian mammoths. This species was huge, even bigger than the more commonly known woolly mammoth.

An ancient bison of a different species was unearthed three years ago in the county, also because of a development project.